This invention relates to a two stage timer control for an automobile window heater electrical power source of the alternator type having a field winding, the control when activated by the operator causing the heater to be energized at full alternator voltage for a predetermined period of time and thereafter at reduced voltage until deactivated by the operator or until the ignition is turned off.
A heating element employed for deicing a rear and front window of an automobile is actuable by a manual switch to cause the same to be operative at a heating level which is limited by a number of conditions. The generation of heat at too rapid a rate will, after the initial melting of ice and evaporation of moisture, cause the glass of the windows to achieve a temperature too high to be safe against temperature shock by sudden cooling. Thus, while it is desirable to have a high rate of heating for a certain period of time to melt ice or snow on the glass window surfaces, it is undesirable to maintain a temperature in the glass higher than that necessary to melt fresh snow falling onto the glass surface after the removal of ice therefrom. Thus two rates of heating are required for an ideal control and operation of window heaters.
It is an object of the invention to provide a direct current timer control device for a window heater of an automobile.
It is another object of the invention to provide a direct current timer especially adapted for use with a window heater energized by an independent alternator driven by the engine of the automobile.
It is another object of the invention to provide a control device for an automobile window heater in which the heater is energized to full alternator voltage for a predetermined period of time upon manual actuation of a heater switch and thereafter without further actuation of said switch said heater is operated at substantially lesser voltage from said alternator.
It is a still further object of the invention to provide a control device for a window heater of the separate alternator driven type having six terminals for connection in automobile circuitry, the latter having an ON-OFF window heater switch, an indicator lamp, an alternator field winding and a resistor normally connected in series with said field winding and a time circuit in said control adapted to shunt said resistance for a predetermined period of time.
Other objects of the invention will be appreciated in more detail by reference to the accompanying drawings.